Fluorescence correlation spectroscopy reveals strong fluorescence quenching of FITC adducts on PEGylated gold nanoparticles in water and the presence of fluorescent aggregates of desorbed thiolate ligands

• Published in: Physical chemistry chemical physics : PCCP Vol. 12; no. 36; pp. 11004 - 11014
• Main Authors: LOUMAIGNE, Matthieu, PRAHO, Raïssa, NUTARELLI, Daniele, WERTS, Martinus H. V, DEBARRE, Anne
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 01.01.2010
• Subjects: Absorption; Analytical chemistry; Chemical Physics; Chemical Sciences; Chemistry; Colloidal state and disperse state; Condensed Matter; Exact sciences and technology; Fluorescein-5-isothiocyanate - chemistry; General and physical chemistry; Gold - chemistry; Ligands; Materials Science; Metal Nanoparticles - chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physics; Polyethylene Glycols - chemistry; Spectrometry, Fluorescence; Sulfur - chemistry; Surface physical chemistry; Water - chemistry; Gold; Correlation; Rayleigh scattering; Nanoparticle; Thiolate; Fluorescence; Suspension; Transition metal; Desorption; Mie scattering; Metal particle; Fluorophore; Dynamics; Imaging; Cross correlation; Fluorescein; Noble metal; Aqueous solution; Aggregate; Colloid particle
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c004167j

Colloidal gold particles functionalised with oligoethylene-glycolated disulfide ligands and fluorescent moieties derived from fluorescein isothiocyanate (FITC) have been prepared and studied in aqueous suspension using fluorescence correlation spectroscopy (FCS). FCS probes the dynamics of the particles at the single object level, and reveals the desorption of fluorescent ligands which subsequently aggregate into larger (slower diffusing) objects. Cross-correlation spectroscopy of the FITC fluorescence and the Rayleigh-Mie scattering (RM-FCCS) of the gold cores shows that the only detectable fluorescent objects are free ligands and aggregates not associated with a gold particle. The fluorescence of bound fluorophores is quenched making their fluorescence too weak to be detected. FCS and RM-FCCS are useful tools for characterising functionalised noble metal particles in solution, under conditions similar to those used in optical bio-imaging. Desorption of thiolates from gold nanoparticles needs to be taken into account when working with these materials at low concentration.